Dynamic random access memory with fully independent partial array refresh function

ABSTRACT

A dynamic random access memory device includes a plurality of memory subblocks. Each subblock has a plurality of wordlines whereto a plurality of data store cells are connected. Partial array self-refresh (PASR) configuration settings are independently made. In accordance with the PASR settings, the memory subblocks are addressed for refreshing. The PASR settings are made by a memory controller. Any kind of combinations of subblock addresses may be selected. Thus, the memory subblocks are fully independently refreshed. User selectable memory arrays for data retention provide effective memory control programming especially for low power mobile application.

FIELD OF THE INVENTION

The present invention relates generally to semiconductor integratedcircuits, and more specifically to dynamic random access memories with apartial array refresh function.

BACKGROUND OF THE INVENTION

In dynamic random access memory (DRAM) integrated circuit devices, aDRAM cell array is typically arranged in rows and columns such that aparticular DRAM cell is addressed by specifying its row and columnwithin the array. A wordline connects a row of cells to a set of bitlinesense amplifiers that detect the data in the cells. In a read operation,a subset of the data in the bitline sense amplifiers is then chosen, or“column-selected” for output. DRAM cells are “dynamic” in the sense thatthe stored data, typically in the form of charged and discharged storagecapacitors, will dissipate after a relatively short period of time.Thus, in order to retain the information, the contents of the DRAM cellsmust be refreshed. The charged or discharged state of the storagecapacitor must be reapplied to an individual memory cell in a repetitivemanner. The maximum amount of time allowable between refreshingoperations is determined by the charge storage capabilities of thestorage capacitors that make up the DRAM cell array. DRAM manufacturerstypically specify a refresh time for which it guarantees data retentionin the DRAM cells.

A refresh operation is similar to a read operation, but no data isoutput. The sensing of the data in the cells by the bitline senseamplifiers is followed by a restoring operation that results in the databeing rewritten to the cells. The data is, thus, “refreshed”. Therefresh operation is performed by enabling a wordline according to a rowaddress, and enabling a bitline sense amplifier. In addition, therefresh operation may be carried out by operating the bitline senseamplifier without receiving an external refresh address. In this case, arefresh address counter, which is integrated in a DRAM device chip,generates a row address subsequent to receiving an external refreshcommand. It is well known that DRAM cells are refreshed by self-refreshfunction to retain stored data. The self-refresh function is one ofperforming refresh operations automatically within the DRAM when in a“standby” mode to retain the data written in its memory cells.

In low power DRAM devices for mobile applications, power consumptionduring a standby or sleep mode is critical. A major portion of powerconsumption during the standby or sleep mode is for refresh operation toretain data. Hence, the key for power reduction during the standby orsleep mode is to reduce the refresh frequency. In low power DRAMdevices, one of the available power reduction features is a partialrefresh that restricts refresh and self-refresh operation during thestandby or sleep mode to a portion of the total memory array. Thisfeature enables the device to reduce refresh current by refreshing onlythat part of the memory array required by a host system. That techniqueis a “partial array refresh” that supports array selections of ¼ array,½ array or ¾ array with fixed array location. For example, a partialarray self-refresh power-saving function with a low power extended moderegister is known (see, for example, Micron® 256 Mb:x32, MOBILE SDRAM,data sheet).

In known partial array self-refresh scheme, a fixed and pre-determinedpartial array selection is performed as per mode register settings. Itdoes not, thus, perform flexible combinations of array selection forpower saving. In DRAM devices which are partitioned as “banks”,“subblocks” or “sub-arrays”, the bank, subblock or sub-array addressesare key performance factors to achieve faster accesses to partial arraymemories. It is a simple solution, without DRAM performance degradation,to limit partial array self-refresh feature in low power DRAM devices.Therefore, the fixed and pre-determined scheme is a good compromisebetween the power saving and the DRAM performance.

A simplified conventional DRAM device is shown in FIG. 1. Referring toFIG. 1 that shows an example DRAM device, a memory controller (notshown) provides it with commands and addresses for DRAM operation. TheDRAM device has a full memory block consisting of four banks 112-0,112-1, 112-2 and 112-3. An external command controller 121, which issynchronized with clocks, includes a command decoder that interprets thecommands and generates a refresh request signal 123 indicating whetherthe memory blocks are to be refreshed or not. The commands include EMRS(extended mode register set) commands. When the EMRS commands are fed tothe external command controller 121, an EMRS signal 125 is provided bythe command decoder thereof.

An extended mode register 131 writes information carried on selectionaddresses “A[0:2]” therein in accordance with mode register set commandsBA[0:1]. The selection addresses “A[0:2]” give instructions for thepartial array self-refresh (PASR) configuration. Once the PASRconfiguration information is written into the extended mode register131, it provides a PASR signal 133, the bits of which indicate whether“full array” should be refreshed or partial array should be refreshed inthe self-refresh mode. In response to the refresh request signal 123 andthe PASR signal 133, an internal bank address counter 135 generates aninternal bank address signal 137 containing internal bank addresses thatare fed to a multiplexer 141.

Also, the mode register set commands BA[0:1] are latched by an externalbank address latch 143. In accordance with the latched addresses, theexternal bank address latch 143 provides an external bank address signal145 containing external bank addresses to the multiplexer 141. Themultiplexer 141 selects the internal bank addresses or the external bankaddresses in response to the refresh request signal 123.

In response to “1” or “0” of the refresh request signal 123, themultiplexer 141 selects the internal bank addresses of the internal bankaddress signal 137 or the external bank addresses of the external bankaddress signal 145. The selected addresses are fed to a bank addressdecoder 151 which in turn provides a decoded address signal 153 to thefull memory block consisting of four banks 112-0, 112-1, 112-2 and112-3. The decoded address signal 153 contains four bank select signals154-0, 154-1, 154-2 and 154-3. Therefore, the bank address decoder 151enables one of the four bank select signals 154-0, 154-1, 154-2 and154-3.

In accordance with the mode register set commands BA[0:1] and theselection addresses “A[0:2]”, the banks are designated as shown infollowing Table 1:

TABLE 1 A[2] A[1] A[0] Banks to be Self-Refreshed 0 0 0 Four Banks 0 0 1Two Banks (e.g., Bank [0] and [1) 0 1 0 One Bank (e.g., Bank [0])

In the DRAM device shown in FIG. 1, the PASR supports only the arrayselections of ¼ array (i.e., one bank), ½ array (i.e., two banks) or ¾array (i.e., three banks) with fixed array location. The DRAM device hasability to save power consumption in the self-refresh mode, however itlacks of controllability of selecting which memory bank will be retainedin the self-refresh mode. Such a low power DRAM design with the EMRSfunction allows a full memory array, a half memory array or a ¼ memoryarray to be selected. When a ¼ memory array is selected for self-refreshmode, for example, the DRAM device enables least significant banks forthe selection of a ¼ memory. It may not, thus, be possible to select theother memory banks for specific data retention. It may also not bepossible to select another combination of banks, for example bank [0]and bank [3], for the self-refresh mode.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an improved dynamicrandom access memory (DRAM) device with an independent partial arrayrefresh function.

In accordance with one aspect, there is provided a dynamic random accessmemory (DRAM) device including a memory having M memory subblocks, Mbeing an integer greater than one. Each subblock has a plurality ofwordlines. Each wordline is connected to a plurality of data storecells. The cells are refreshed by refresh operation. Also, the DRAMdevice includes a refresh circuit for controlling in a refresh mode therefreshing of the memory subblocks in accordance with M subblock refreshdata independently set.

Advantageously, the refresh circuit includes a configuration circuit forconfiguring the M subblock refresh data in response to input data. The Msubblock refresh data is independently set by the input data. Forexample, the configuration circuit includes a latch circuit for holdingthe input data. The M subblock refresh data is produced in accordancewith the held input data. The latch circuit may include M latchingcircuits for latching the M subblock refresh data. Each of the Mlatching circuit latches the respective one of the M subblock refreshdata independently.

In accordance with another aspect, there is provided a method forrefreshing a dynamic random access memory device including M memorysubblocks, M being an integer greater than one, each subblock having aplurality of wordlines, each wordline being connected to a plurality ofdata store cells, the cells being refreshed in a refresh mode. Themethod including controlling in a refresh mode the refreshing of thememory subblocks in accordance with M subblock refresh dataindependently set.

For example, the step of controlling includes the step of configuringthe M subblock refresh data in response to input data, the M subblockrefresh data being independently set by the input data. The step ofconfiguring includes the step of holding the input data, the M subblockrefresh data being produced in accordance with the held input data.

Advantageously, the method further includes the step of providing anaddress signal for selecting the subblock.

In accordance with a further aspect, there is provided a refreshcontroller for use in a dynamic random access memory device selectivelyoperated in a refresh mode and a non self-refresh mode, the DRAM deviceincluding M memory subblocks, M being an integer greater that one. Eachsubblock has a plurality of wordlines. Each wordline is connected to aplurality of data store cells. The cells are refreshed in a refreshmode. The refresh controller includes a refresh circuit for controllingin refresh mode the refreshing of the memory subblocks in accordancewith M subblock refresh data independently set.

Advantageously, the refresh controller further includes a configurationcircuit for configuring the M subblock refresh data in response to inputdata, the M subblock refresh data being independently set by the inputdata.

For example, the configuration circuit includes a latch circuit forholding the input data, the M subblock refresh data being produced inaccordance with the held input data.

In accordance with embodiments of the present invention, there isprovided a DRAM device and a method for refreshing memory cells fullyindependent partial array refresh and self-refresh based on minimumcompliable array size. Any kind of array combination can be selected andrefreshed by input data selection. In the embodiments, unlimitedcontrollability of array selection is achieved for refresh andself-refresh. Configurable partial array registration is performed bydata input. The embodiments of the present invention achieve advantages;flexibility of selection of memory array blocks; unlimited combinationof arrays for refresh and self-refresh; user selectable arrays for dataretention provides effective memory control programming especially forlow power mobile application.

Other aspects and features of the present invention will become apparentto those ordinarily skilled in the art upon review of the followingdescription of specific embodiments of the invention in conjunction withthe accompanying figures.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will now be described, by way ofexample only, with reference to the attached Figures, wherein:

FIG. 1 is a schematic diagram illustrating a conventional addresscontroller found in a dynamic random access memory (DRAM) device with apartial array self-refresh function;

FIG. 2 is a schematic diagram illustrating a DRAM device according toone embodiment of the present invention;

FIG. 3 is a schematic diagram illustrating a DRAM device according to anembodiment of the present invention;

FIG. 4 is a schematic diagram illustrating a detailed circuit of apartial array self-refresh (PASR) configuration register shown in FIG.3;

FIG. 5 is a schematic diagram illustrating a detailed circuit of anexternal address decoder shown in FIG. 3;

FIG. 6 is a schematic diagram illustrating a detailed circuit of aninternal address decoder shown in FIG. 3;

FIG. 7 is a schematic diagram illustrating a detailed circuit ofsubblock selectors and a memory shown in FIG. 3;

FIG. 8 is a schematic diagram illustrating an example of the addressingof the subblocks of the memory shown in FIG. 3;

FIG. 9 is a flowchart illustrating the operation of the DRAM deviceshown in FIG. 3;

FIG. 10 is a flowchart illustrating the self-refresh operation of theDRAM device shown in FIG. 3;

FIG. 11 is a flowchart illustrating the normal operation of the DRAMdevice shown in FIG. 3;

FIG. 12 is a schematic diagram illustrating a DRAM device according toanother embodiment of the present invention;

FIG. 13 is a schematic diagram illustrating a detailed circuit of a PASRconfiguration register shown in FIG. 12;

FIG. 14 is a schematic diagram illustrating a detailed circuit of aselector and an address decoder shown in FIG. 12;

FIG. 15 is a schematic diagram illustrating a detailed circuit of asubblock selectors and a memory shown in FIG. 12; and

FIG. 16 is a flowchart illustrating the operation of the DRAM deviceshown in FIG. 12.

DETAILED DESCRIPTION

In the following detailed description of sample embodiments of theinvention, reference is made to the accompanying drawings which form apart hereof, and in which is shown by way of illustration specificsample embodiments in which the present invention may be practiced.These embodiments are described in sufficient detail to enable thoseskilled in the art to practice the present invention, and it is to beunderstood that other embodiments may be utilized and that logical,mechanical, electrical, and other changes may be made without departingfrom the scope of the present invention. The following detaileddescription is, therefore, not to be taken in a limiting sense, and thescope of the present invention is defined by the appended claims.

Generally, the present invention provides the refreshing of memory cellswithin an array included in a dynamic random access memory (DRAM)device. The present invention applied to a DRAM device will now bedescribed, the DRAM device having the function of refreshing DRAM cells.Embodiments according to the present invention will be described DRAMdevices performing the self-refresh function, that is, a partial arrayself-refresh (PASR). Some embodiments of the present invention will alsobe applicable to the normal refresh function, that is, a partial arrayrefresh (PAR). FIG. 2 shows a DRAM device according to one embodiment ofthe present invention. Referring to FIG. 2, a data input signal 201containing subblock selection input data DIN[1:M] is provided to apartial array refresh (PAR) configuration register 203. The PARconfiguration register 203 includes M latches 204-1-204-M. The subblockselection input data DIN includes M data corresponding to the number ofmemory subblocks. M is an integer greater than one. The PARconfiguration register 203 provides a PAR setting signal 207 to asubblock address controller 209. A refresh signal “REFRESH” 208 isprovided to the subblock address controller 209. In response to therefresh signal 208, a first address producer 210 produces a firstaddress (e.g., an internal address) signal 211 represented by N bitsthat is provided to the subblock address controller 209. In someembodiments, each permutation of the N bits (e.g., four bits) isassociated with one of the M subblocks (e.g., 16 subblocks). Also, asecond address producer 216 produces a second address (e.g., an externaladdress) signal 213 represented by N bits that is provided to thesubblock address controller 209. The subblock address controller 209provides a subblock address signal 217 to a memory 219 that is dividedto M subblocks 220-1-220-M. When the refresh signal 208 indicates therefresh mode, the internal address signal 211 is provided.

Each of the M data in the subblock selection input data DIN is latchedor held in the respective one of the M latches 204-1-204-M. The latches204-1-204-M produce M PAR configuration data of the PAR setting signal207. In response to the refresh signal 208, the subblock addresscontroller 209 produces the subblock addresses SubAd[1;M] to becontained in the subblock address signal 217, in accordance with thesecond address signal 213 or with the PAR setting signal 207 and thefirst address signal 211. More particularly, if the refresh signal 208is in the “REFRESH” state, then the first address signal 211 is used,and otherwise the second address signal 213 is used. The producedsubblock addresses designate or select memory subblocks to be refreshedfrom the subblocks 220-1-220-M. When the refresh signal 208 representsthe self-refresh request, the designated subblocks 220-1-220-M of thememory 219 are self-refreshed. When the subblock address signal 217represents the normal refresh request, the designated subblocks220-1-220-M of the memory 219 are refreshed during the normaloperations. The subblock selection input data DIN of the data inputsignal 201 is independently set in the latches 204-1-204-M of the PARconfiguration register 203. The data of the PAR setting signal 207 isindependently set from the others. The subblocks 220-1-220-M of thememory 219 are independently designated or selected. Thus, a fullyindependently partial array refresh function is achieved.

More detailed embodiments of DRAM devices will be described. In thefollowing embodiments according to the present invention, the logic“high” and “low” states of the signals are represented by two differentvoltages V1 and V2 (<V1). For example, the voltages V1 and V2 are “high”and “low” supply voltages VDD and VSS, respectively.

FIG. 3 shows a DRAM device according to an embodiment of the presentinvention. The DRAM device includes a memory that has 16 memorysubblocks. In the embodiment, for example, the address data in the formof subblock selection input SubAd[1:16] is provided from pins (notshown) of 16 bits that correspond to 16 different memory subblocks of afull memory block of a DRAM. Each data input pin is associated with arespective subblock of the memory.

Referring to FIG. 3, an external command controller 221 including acommand decoder 222, which is synchronous with the clocks of a clocksignal 223, receives a command signal 225 including commands “/RAS”,“/CAS”, “/WE”, “/CS”. The command decoder 222 interprets the commandsand provides a configuration control clock signal 227 to a partial arrayself-refresh (PASR) configuration register 231 for writing the PASRconfiguration information thereinto. Also, the external commandcontroller 221 provides a refresh request signal 229 to an internaladdress counter 233 and a subblock selector 241. The PASR configurationregister 231 receives a data input signal 247 that contains subblockselection input data DIN[1:16]. The PASR configuration register 231includes 16 flip-flops for latching the subblock selection input dataDIN[1:16]) and provides a PASR signal 251 including PASR configurationregister set commands. Each signal containing the PASR configurationregister set command is an active “high” signal.

In some embodiments, the refresh request signal 229 is a self-refreshmode signal. The self-refresh mode signal is provided by the externalcommand controller 221 upon an entry to and an exit from theself-refresh. In the self-refresh mode operation, an internallygenerated address (for rows or words) is output by the internal addresscounter 233.

The internal address counter 233 generates a four-bit internal addresssignal “IA[0:3]” 255 in response to the refresh request signal 229. Theinternal address signal 255 is provided to an internal address decoder237. Each bit signal of the internal address signal 255 is a repetitivepulse signal having a respective predetermined repetition period and apredetermined pulse width. The internal address decoder 237 provides adecoded internal address signal 256 containing 16 decoded internaladdresses InAd[1:16] to the subblock selector 241. A four-bit externaladdress signal “ADDR[0:3]” 261 is provided to an external address latch263 that latches the addresses ADDR[0:3], synchronizing with a clocksignal “CLK” 265. The external address latch 263 provides four-bitexternal address signal “EA[0:3]” 267 to an external address decoder 239which provides a decoded external address signal 268 containing 16decoded external addresses “ExAd[1:16]” to the subblock selector 241.

In response to the refresh request signal 229, the subblock selector 241selects the decoded external address signal 268 or the decoded internaladdress signal 256 and provides a subblock address signal 271 to amemory 280. The memory 280 includes 16 subblocks. The memory 280 has aplurality of wordlines, bitlines and data cells (not shown).

FIG. 4 shows a detailed circuit of the PASR configuration register 231shown in FIG. 3. Referring to FIG. 4, the PASR configuration register231 includes 16 D type flip-flops (D-FFs) 245-1-245-16, the D inputs ofwhich receive respective data input signal 338-1-338-16 included in thedata input signal 247. The configuration control clock signal 227 iscommonly fed to the clock inputs CK of the D-FFs 245-1-245-16. The 16D-FFs 245-1-245-16 provide 16 PASR bit signals 342-1-342-16 included inthe PASR signal 251.

Following Table 2 shows the relation between the subblock selectioninput data DIN[1]-DIN[16] and the partial array self-refresh (PASR)settings.

TABLE 2 Subblock Selection Partial Array Input Data Self-Refresh DINPASR DIN[1] PASR[1] DIN[2] PASR[2] DIN[3] PASR[3] DIN[4] PASR[4] DIN[5]PASR[5] DIN[6] PASR[6] DIN[7] PASR[7] DIN[8] PASR[8] DIN[9] PASR[9]DIN[10] PASR[10] DIN[11] PASR[11] DIN[12] PASR[12] DIN[13] PASR[13]DIN[14] PASR[14] DIN[15] PASR[15] DIN[16] PASR[16]

FIG. 5 shows a detailed circuit of the internal address decoder 237shown in FIG. 3. Referring to FIG. 5, the internal address signal 255contains four internal addresses IA[0], IA[1], IA[2] and IA[3]represented by four internal address bit signals 345-0, 345-1, 345-2 and345-3 that are fed to 16 AND gates 371-1-371-16, each having four inputsI0, I1, I2 and I3. The AND gates 371-1-371-16 provide 16 internal outputbit signals 373-1-373-16 that are fed to 16 AND gates 375-1-375-16.Also, the PASR signal 251 includes 16 PASR bit signals 342-1-342-16 thatare fed to the 16 AND gates 375-1-375-16. The 16 AND gates 375-1-375-16provides 16 decoded internal address bit signals 347-1-347-16 includedin the decoded internal address signal 256.

Following Table 3 shows the relation between the internal address bitsIA[0:3] and the internal address output IAO[1:16] to be logic “high”. Inthe following table, “0” and “1” represent logic “low” and “1”,respectively.

TABLE 3 IA3 IA2 IA1 IA0 IAO to be “High” 0 0 0 0 IAO[1] 0 0 0 1 IAO[2] 00 1 0 IAO[3] 0 0 1 1 IAO[4] 0 1 0 0 IAO[5] 0 1 0 1 IAO[6] 0 1 1 0 IAO[7]0 1 1 1 IAO[8] 1 0 0 0 IAO[9] 1 0 0 1 IAO[10] 1 0 1 0 IAO[11] 1 0 1 1IAO[12] 1 1 0 0 IAO[13] 1 1 0 1 IAO[14] 1 1 1 0 IAO[15] 1 1 1 1 IAO[16]

In order to perform the logic operation as shown in above Table 3, theAND gates 371-1-371-16 have predetermined inverting inputs. For example,the AND gate 371-1 has four inverting inputs I0, I1, I2 and I3. The ANDgate 371-2 has three inverting inputs I1, I2 and I3. Similarly, the ANDgate 371-15 has one inverting inputs I0. The AND gate 371-16 has noinverting inputs.

Following Table 4 shows the relation between PASR to be logic “high”,IAO to be logic “high” and the subblock to be designated or selected inthe memory 280.

TABLE 4 PASR IAO Subblock to be “High” to be “High” to be SelectedPASR[16] IAO[16] Subblock[16] PASR[15] IAO[15] Subblock[15] PASR[14]IAO[14] Subblock[14] PASR[13] IAO[13] Subblock[13] PASR[12] IAO[12]Subblock[12] PASR[11] IAO[11] Subblock[11] PASR[10] IAO[10] Subblock[10]PASR[9] IAO[9] Subblock[9] PASR[8] IAO[8] Subblock[8] PASR[7] IAO[7]Subblock[7] PASR[6] IAO[6] Subblock[6] PASR[5] IAO[5] Subblock[5]PASR[4] IAO[4] Subblock[4] PASR[3] IAO[3] Subblock[3] PASR[2] IAO[2]Subblock[2] PASR[1] IAO[1] Subblock[1]

FIG. 6 shows a detailed circuit of the external address decoder 239shown in FIG. 3. Referring to FIG. 6, the external address signal 267contains four external addresses EA[0], EA[1], EA[2] and EA[3]represented by four external address bit signals 357-0, 357-1, 357-2 and357-3 that are fed to 16 AND gates 364-1-364-16. The AND gates364-1-364-16 provide 16 decoded external address bit signals359-1-359-16 included in the decoded external address signal 268.Following Table 5 shows the relation between the internal address IAbits and the subblock to be designated or selected in the memory 280. Inthe following table, “0” and “1” represent logic “low” and “1”,respectively.

TABLE 5 EA[3] EA[2] EA[1] EA[0] Subblock 0 0 0 0 [1] 0 0 0 1 [2] 0 0 1 0[3] 0 0 1 1 [4] 0 1 0 0 [5] 0 1 0 1 [6] 0 1 1 0 [7] 0 1 1 1 [8] 1 0 0 0[9] 1 0 0 1 [10] 1 0 1 0 [11] 1 0 1 1 [12] 1 1 0 0 [13] 1 1 0 1 [14] 1 11 0 [15] 1 1 1 1 [16]

In order to perform the logic operation as shown in above Table 5, theAND gates 364-16, 364-15, and 364-1 have predetermined inverting inputswhich are identical to the inverting inputs of the AND gates 371-16,371-15, and 371-1 shown in FIG. 5.

FIG. 7 shows detailed circuits of the subblock selector 241 and thememory 280 shown in FIG. 3. Referring to FIG. 7, the decoded externaladdress bit signals 359-1-359-16 included in the decoded externaladdress signal 268 and the decoded internal address bit signals347-1-347-16 included in the decoded internal address signal 256 are fedto 16 selection logic circuits 421-1-421-16 included in the subblockselector 241. The 16 selection logic circuits 421-16-421-16 are the samecircuit structure and each of them has two NAND gates and one NOR gate.

The refresh request signal 229 and its inverted signal 419 by aninverter 418 are fed to the 16 selection logic circuits 421-1- and421-16. In the selection logic circuit 421-16, a NAND gate 431-16receives the decoded internal address bit signal 347-16 and the refreshrequest signal 229 and a NAND gate 433-16 receives the decoded externaladdress bit signal 359-16 and the inverted signal 419. Two logic outputsignals from the NAND gates 431-16 and 433-16 are fed to a NOR gate435-16 which in turn provides a subblock bit signal 439-16. Similarly,the selection logic circuit 421-15 includes a NAND gate 431-15 thatreceives the external address bit signal 357-15 and the refresh requestsignal 229 and a NAND gate 433-15 receives the decoded external addressbit signal 359-15 and the inverted signal 419. Two logic output signalsfrom the NAND gates 431-15 and 433-15 are fed to a NOR gate 435-15 whichin turn provides a subblock bit signal 439-15. In the selection logiccircuit 421-1, a NAND gate 431-1 receives the external address bitsignal 357-1 and the refresh request signal 229. A NAND gate 433-1receives the decoded external address bit signal 359-1 and the invertedsignal 419. Two logic output signals from the NAND gates 431-1 and 433-1are fed to a NOR gate 435-1 which in turn provides a subblock bit signal439-1. The 16 subblock bit signals 439-1-439-16 are included in thesubblock address signal 271.

The memory 280 includes 16 subblocks 441-1-441-16 that receive thesubblock bit signals 439-1- and 439-16, respectively. The memory 280 hasa plurality of wordlines, bitlines and data cells (not shown). Thesubblock 441-1 has wordlines WL-1-WL-N. The subblock 441-2 has wordlinesWL-(N+1)-WL-2N. The subblock 441-15 has wordlines WL-(14N+1)-WL-15N. Thesubblock 441-16 has wordlines WL-(15N+1)-WL-16N.

FIG. 8 shows an example of the addressing in the DRAM device shown inFIG. 3. Referring to FIG. 8, the PASR signal 251 contains thePASR[1]-PASR[16] to address the 16 subblocks 441-1-441-16 of the memory280.

Referring to FIGS. 3-8, the PASR configuration register 231 generates 16different signal bits which are called here the PASR signal “PASR[1:16]”251. The 16-bit signals enable or disable any one of the 16 memorysubblocks including the subblocks 441-1-441-16 through the selectionlogic circuit 421-1-421-16. If, for example, PASR[1] is set logically“high”, the subblock[1] 441-1 of the memory 280 is to be refreshed. IfPASR[1] is set logically “low”, the subblock[1] 441-1 is to benon-refreshed, so that data may be lost therein.

FIG. 9 shows the operation of the DRAM device shown in FIG. 3. Referringto FIGS. 3-9, in the operation mode, the memory controller (not shown)provides the subblock selection input data DIN[1:16] as the data inputsignal 247 to the DRAM device (i.e., the PASR configuration register231). The subblock selection input data DIN[1:16] is provided and thePASR configuration register set commands are latched in the D-FFs245-1-245-16 (step 511). The command decoder 222 of the external commandcontroller 221 decodes the commands of the command signal 225 (step512). In a case where a self-refresh entry command is detected (YES atstep 513), the self-refresh operation is performed (step 514). Until aself-refresh exit command is detected by the external command controller221 (YES at step 515), the self-refresh operation is performed (step514). In a case where a self-refresh entry command is not detected (NOat step 513) or a self-refresh exit is detected (YES at step 515), it isdetermined whether the DRAM device is in a deep power down mode (step516). If no deep power down command is detected by the command decoder222 (NO at step 516), the normal operation is performed (step 517).Thereafter, the above operations at steps 512-516 are repeated. If theDRAM device is, however, in a deep power down mode (YES at step 516),that is, a deep power down command is detected by the command decoder222, the operation of the DRAM device will be disabled.

FIG. 10 shows the self-refresh operation of the DRAM device at step 514shown in FIG. 9. Referring to FIGS. 2-10, the subblock selection inputdata DIN[1:16] are already latched in the 16 D-FFs 245-1-245-16 of thePASR configuration register 231 (step 511) and the PASR configurationregister 231 produces the PASR signal 251 (step 521). The internaladdress counter 233 generates the internal address signal “IA[0:3]” 255and the internal address decoder 237 produces the decoded internaladdress signal “InAd[1:16]” 256 (step 522). In response to the refreshrequest signal 229, the subblock address signal 271 containing thesubblock addresses SubAd[1:16] is produced and the subblock selector 241selects the subblocks 441-1-441-16 of the memory 280 (step 523). In theselected subblock(s) from the subblocks 441-1-441-16, with theself-refresh operation, known address controlling operation is performedto select the wordlines WLs to which the DRAM cells are connected arerefreshed (step 524).

FIG. 11 shows the normal operation of the DRAM device at step 517 shownin FIG. 9. Referring to FIGS. 2-11, the external address latch 263latches ADDR[0:3] of the external address signal 261 (step 531) andprovides EA[0:3] of the external address signal 267. The externaladdress decoder 239 decodes EA[0:3] (step 532) and the decoded addressesExAd[1:16] of the decoded external address signal 268 are provided tothe subblock selector 241 (step 533). The subblock selector 241 selectsthe decoded external addresses ExAd[1:16] of the decoded externaladdress signal 268 are selected and the subblock selector 241 selectsthe subblocks 441-1-441-16 of the memory 280 (step 534). Then, thenormal memory access operation is performed (step 535).

For example, when PASR[16] is set logically “high”, which means that thesubblock[16] is to be refreshed. In response to the PASR bit signal342-16 (“high”), the AND gate 375-16 passes the internal output bitsignal 373-16 “IAO[16]” as the decoded internal address bit signal347-16 (“InAd[16]”). With the “high” logic state of the refresh requestsignal 229, the decoded internal address bit signal 347-16 is invertedby the NAND gate 431-16 and re-inverted by the NOR gate 435-16 of theselection logic circuit 421-16. Thus, the internal address InAd[16] ofthe decoded internal address bit signal 347-16 is provided as thesubblock bit signal 439-16. The “high” state of the decoded internaladdress InAd[16] allows the subblock 441-16 to be refreshed during theself-refresh period. If the refresh request signal 229 is logic “low”,the NAND gates 431-16-431-1 of the selection logic circuits 421-16-421-1do not pass the internal addresses InAd[16:1] of the decoded internaladdress bit signals 347-16-347-1 and the external addresses ExAd[16:1]of the decoded external address bit signal 359-16-359-1 are forwarded bythe subblocks 441-16-441-1 to the memory 280.

In accordance with settings of the PASR configuration register 231, thepartial array refresh is varied. Following Table 6 shows the settings(logic states) of the PASR configuration register 231 for refreshingsubblock[1] to subblock[6] in the self-refresh mode. In the followingtables, “L” and “H” represent logic “low” and “high”, respectively.

TABLE 6 PASR [16] [15] [14] [13[ [12] [11] [10] [9] [8] [7] [6] [5] [4][3] [2] [1] Logic L L L L L L L L L L H H H H H H State

In accordance with the above settings, the sequence of the self-refreshissubblock[6]→subblock[5]→subblock[4]→subblock[3]→subblock[2]→subblock[1].The sequence operation is performed in response to the repetitive pulsesof the address signal.

Following Table 7 shows the settings of the PASR configuration register231 for refreshing subblock[1], subblock[8] and subblock in theself-refresh mode.

TABLE 7 PASR [16] [15] [14] [13[ [12] [11] [10] [9] [8] [7] [6] [5] [4][3] [2] [1] Logic H L L L L L L L H L L L L L L H State

In accordance with the above settings, the sequence of the self-refreshis subblock[16]→subblock[8]→subblock[1].

Following Table 8 shows the settings of the PASR configuration register231 for refreshing subblock[1] to subblock[16] in the self-refresh mode.

TABLE 8 PASR [16] [15] [14] [13[ [12] [11] [10] [9] [8] [7] [6] [5] [4][3] [2] [1] Logic H H H H H H H H H H H H H H H H State

In accordance with the above settings, the sequence of the self-refreshissubblock[16]→subblock[15]→subblock[14]→subblock[13]→subblock[12]→subblock[11]→subblock[10]→subblock[9]→subblock[8]→subblock[7]→subblock[6]→subblock[5]→subblock[4]→subblock[3]→subblock[2]→subblock[1].

Following Table 9 shows the settings of the PASR configuration register231 for not refreshing any subblocks in the self-refresh mode.

TABLE 9 PASR [16] [15] [14] [13[ [12] [11] [10] [9] [8] [7] [6] [5] [4][3] [2] [1] Logic L L L L L L L L L L L L L L L L State

In summary, for the particular implementation described, while in theself-refresh mode, the memory's subblock that is refreshed is selectedby the logical combination of the PASR configuration register 231 andthe decoded address from the internal address counter 233.

In accordance with the subblock selection input data DIN[1:M]represented by the data input signal 201, separate PASR settings(PASR[1:16]) are provided for the respective ones of the subblock441-1-441-16, with the results that the fully independentcontrollability of multiple memory subblocks' partial refresh isperformed. As such, the same number of dedicated partial array refreshsignals as that of memory sub-arrays is very efficient way to providethe maximum controllability of power saving in a standby or sleep modeas well as maximum flexibility of memory usage in performance point ofview.

FIG. 12 shows a DRAM device according to another embodiment of thepresent invention. The DRAM device includes a memory that has 16 memorysubblocks. In the embodiment, for example, the data is provided frompins of 16 bits that correspond to 16 different memory subblocks of afull memory block of a DRAM. Each data input pin is associated with arespective subblock of the memory.

Referring to FIG. 12, an external command controller 611 including acommand decoder 612, which is synchronous with the clocks of a clocksignal 613, receives a command signal 615 including commands “/RAS”,“/CAS”, “/WE”, “/CS”. The command decoder 612 interprets the commandsand provides a configuration control clock signal 617 to a PASRconfiguration register 621 for writing configuration registrationinformation thereinto. Also, the external command controller 611provides a refresh request signal 619 to an internal address counter 623and an address selector 629. The PASR configuration register 621receives a data input signal 637 containing the subblock selection inputdata DIN[1:16]. The PASR configuration register 621 includes 16flip-flops for latching the subblock selection input data DIN[1:16]) andprovides a PASR signal 641 including PASR configuration register setcommands “PASR[1:16]”. The internal address counter 623 generates afour-bit internal address signal 645 “IA[0:3]” to the address selector629. Each bit signal of the internal address signal 645 is a repetitivepulse signal having predetermined repetition period and a predeterminedpulse width. A four-bit external address signal “ADDR[0:3]” 651 isprovided to an external address latch 653 that latches ADDR[0:3]synchronizing with the clocks of a clock signal 655 “CLK”. The externaladdress latch 653 provides four-bit external address signal “EA[0:3]”657 to the address selector 629.

In response to the refresh request signal 619, the address selector 629selects the internal address signal 645 or the external address signal657 and provides a selected address signal “SeAd[0:3]” 646 to an addressdecoder 631. The address decoder 631 provides a 16-bit decoded addresssignal “DeAd[1:16]” 671 to subblock selector 670 that receives the PASRsignal 641. The subblock selector 670 provides a subblock address signal“SubAd[1:16]” 673 to a memory 680 including 16 subblocks. The memory 680has a plurality of wordlines, bitlines and data cells. The externalcommand controller 611, the internal address counter 623 and theexternal address latch 653 correspond to the external command controller221, the internal address counter 233 and the external address latch 263shown in FIG. 3, respectively.

FIG. 13 shows a detailed circuit of the PASR configuration register 621shown in FIG. 12. Referring to FIG. 13, the PASR configuration register621 includes 16 D-FFs 745-1-745-16, the D inputs of which receiverespective data input signal 638-1-638-16 (containing the subblockselection input data DIN[1:16]) included in the data input signal 637.The configuration control clock signal 617 is commonly fed to the clockinputs CK of the D-FFs 745-1-745-16. The 16 D-FFs 745-1-745-16 provide16 PASR bit signals 742-1-742-16 included in the PASR signal 641.

FIG. 14 shows a detailed circuit of the address selector 629 and theaddress decoder 631 shown in FIG. 12. Referring to FIG. 14, the addressselector 629 includes four multiplexers 721-0-721-3. The externaladdress signal 657 includes four external address bit signals757-0-757-3 representing EA[0:3] and the internal address signal 645includes 4 internal address bit signals 745-0-745-3 representingIA[0:3]. The external address bit signals 757-0, 757-1, 757-2 and 757-3and the internal address bit signals 755-0, 755-1, 755-2 and 755-3 arefed to the multiplexers 721-0-721-3, respectively. Also, themultiplexers 721-0-721-3 receive the refresh request signal 619. Whenthe refresh request signal 619 is logic “high”, the multiplexers721-0-721-3 select the internal address bit signals 755-0-745-3 and whenthe refresh request signal 619 is logic “0”, the multiplexers721-0-721-3 select the external address bit signals 757-0-757-3. Theselected address bit signals “SeAd[0:3]” 722-0-722-3 included in theselected address signal 646 from the multiplexers 721-0-721-3 are fed to16 AND gates 764-1-764-16 included in the address decoder 631. The ANDgates 764-1-764-16 provide 16 decoded address bit signals “DeAd[:16]”759-1-759-16 included in the decoded address signal 671. Each of the ANDgates 764-1-764-16 has four predetermined inverting or non-invertinginputs I0-I3 which are the same as those of the AND gates 371-1-371-16shown in FIG. 5.

FIG. 15 shows a detailed circuit of the subblock selector 670 and thememory 680 shown in FIG. 12. Referring to FIG. 15, the subblock selector670 includes 16 AND gates 775-1-775-16, each having two inputs. Oneinputs of the AND gates 775-1-775-16 receive the decoded address bitsignals “DeAd[1:16]” 759-1-759-16, respectively. Similarly, the otherinputs of the AND gates 775-1-775-16 receive the PASR bit signals742-1-742-16, respectively. The logic outputs from the AND gates775-1-775-16 are 16 subblock bit signals 747-1-747-16 included in thesubblock address signal 673. The subblock addresses SubAd[1:16]represented by the 16 subblock bit signals 747-1-747-16 are fed to the16 subblocks 741-1-741-16 of the memory 680, respectively. The 16subblocks 741-1-741-16 form as a memory having a plurality of wordlines,bitlines and data cells. In this embodiment, the memory is divided tothe 16 subblocks 741-1- - - - -741-16. Thus, the subblock 741-1 haswordlines WL-1-WL-N. The subblock 741-2 has wordlines WL-(N+1)-WL-2N.The subblock 741-15 has wordlines WL-(14N+1)-WL-15N. The subblock 741-16has wordlines WL-(15N+1)-WL-16N. The PASR configuration register 621generates 16 different signal bits, that is, the PASR signal 641“PASR[1:16]”. The 16-bit signals enable or disable any one of the 16memory subblocks including the subblocks 741-11-741-16 through thesubblock selector 670.

FIG. 16 shows the operation of the DRAM device shown in FIG. 12.Referring to FIGS. 12-16, in the operation mode, the memory controller(not shown) provides the subblock selection input data DIN[1:16] as thedata input signal 637 to the DRAM device (i.e., the PASR configurationregister 621). The subblock selection input data DIN[1:16] is providedand the PASR configuration register set commands are latched in theD-FFs 745-1-745-16 (step 811). The command decoder 612 of the externalcommand controller 611 decodes the commands of the command signal 615(step 812). In a case where a self-refresh entry command is detected(YES at step 813), the refresh request signal 619 is provided by theexternal command controller 611. In response to the refresh requestsignal 619, the internal address counter 623 generates the four-bitinternal address signal 645 (“IA[0:3]”) including the four internaladdress bit signals 755-0-75-3 (step 814). The address selector 629having the multiplexers 721-0-721-3 selects IA[0:3] and provides it asthe selected addresses SeAd[0:3] represented by the four selectedaddress bit signals 722-0-722-3 of the selected address signal 646 (step815). The selected addresses SeAd[0:3] are decoded by the addressdecoder 631 including the 16 AND gates 764-1-764-16 and the decodedaddresses DeAd[1:16] represented by the 16 decoded address bit signals759-1-759-16 of the decoded address signal 671 are provided (step 816).

The subblock selection input data DIN[1:16] are already latched in the16 D-FFs 745-1-745-16 of the PASR configuration register 621 (step 811)and the PASR configuration register 621 produces the PASR signal 641(step 817). The subblock selector 670 (the AND gates 775-1-775-16)provides 16 subblock address bit signals 747-1-747-16 (the subblockaddresses “SubAd[1:16]” of the subblock address bit signals747-1-747-16) based on the decoded addresses DeAd[1:16] and the PASRsettings PASR[1:16]. The subblocks 741-1-741-16 of the memory 680 areselected in accordance with the subblock addresses SubAd[1:16] (step818). Then, the self-refresh operation is performed (step 819). If noself-refresh exit command is detected (NO at step 820), the aboveoperations at steps 815-819 are repeated. If a self-refresh exit commandis detected (YES at step 820), then it will be determined whether theDRAM device enters into a deep power down mode (step 821). If no deeppower down command is detected by the command decoder 612 (NO at step821), the operation will return to step 812 and the above operationswill be repeated. If a deep power down mode enters (YES at step 821),the DRAM device will be disabled.

When no self-refresh entry is detected (NO at step 813), the externaladdress latch 653 provides the external addresses EA[0:3] represented bythe external address signal 657 (step 831). The address selector 629selects the external address signal 657 (step 832) and provides theselected address signal 646 (as the decoded address DeAd[1:16]) (step833). The subblock selector 670 provides the subblock addressesSubAd[1:16] represented by the subblock address signal 673 (step 834).Then, the normal access operation is performed (step 835). Thereafter,it is determined whether the DRAM device enters a deep power down mode(step 821).

In above embodiments, the refresh operation in DRAM devices is a“self-refresh”. However, the partial array refresh scheme describedabove is also applicable to a normal refresh. Implementation of fullyindependent partial array refresh scheme into DRAM control logic orprograms maximizes the flexibility of memory cell array usage betweennormal access modes and refresh/self-refresh access modes. In theapplication of the normal refresh, the PASR configuration and functionbecome as PAR (partial array refresh) configuration and function. Theembodiment DRAM devices have advantages of flexibility of memory arrayblock selection, any combination of arrays for refresh and self-refresh.User selectable arrays for data retention provide effective memorycontrol, especially for low power mobile application.

The embodiments described above may have further various variations. Thenumber of subblocks of a memory is not limited to 16. A memory may bedivided by M subblocks (M is an integer greater than one). It is, thus,at least M values of the subblock selection input data DIN are requiredfor the PASR or PAR signal to designate the M subblocks. The addresssignals are not limited to four-bit signals. N (an integer) bits arerequired for addressing the M subblocks.

In the above described embodiments, the signals are active “high” logicsignals. The signals may, however, be active “low” signals, according todesign preferences. The logic “high” and “low” states of the signals maybe represented by the low and high supply voltages VSS and VDD,respectively. Also, the voltages with the DRAM device operates may bevoltages derived from the “high” and “low” supply voltages VDD and VSS.PASR or PAR signals can be active “low” as well as active “high”. A PASRor PAR configuration register can have address signals as register data.Dynamic decoding scheme can be used for decoders.

In the embodiments described above, the device elements and circuits areconnected to each other as shown in the figures, for the sake ofsimplicity. In practical applications of the present invention tosemiconductor ICs and DRAM devices, elements, circuits, etc. may beconnected directly to each other. As well, elements, circuits etc. maybe connected indirectly to each other through other elements, circuits,etc., necessary for operation of the semiconductor ICs and DRAM devices.Thus, in actual configuration of semiconductor ICs and DRAM devices, thecircuit elements and devices are coupled with (directly or indirectlyconnected to) each other.

The above-described embodiments of the present invention are intended tobe examples only. Alterations, modifications and variations may beeffected to the particular embodiments by those of skill in the artwithout departing from the scope of the invention, which is definedsolely by the claims appended hereto.

1-30. (canceled)
 31. A dynamic random access memory (DRAM) device,comprising: a plurality memory banks each having a plurality ofwordlines, each of the plurality of wordlines being connected to aplurality of data store cells that are refreshable in a self-refreshmode; and storage for storing a bit corresponding to each of theplurality of memory banks, each bit indicating whether or not thecorresponding memory bank is to be refreshed in the self-refresh mode;wherein, in the self-refresh mode, the DRAM device performs aself-refresh operation only for memory banks for which the correspondingbits indicate that the memory banks are to be refreshed.
 32. The DRAMdevice of claim 31, wherein the storage for storing a bit correspondingto each of the plurality of memory banks comprises a register.
 33. TheDRAM device of claim 31, wherein the register comprises a plurality oflatches, each latch storing a bit corresponding to one of the pluralityof memory banks.
 34. The DRAM device of claim 31, further comprising: afirst address producing circuit configured to produce a first addresssignal in the self-refresh mode; and a second address producing circuitconfigured to produce an external address signal.
 35. The DRAM device ofclaim 34, further comprising a subblock address controlling circuitconfigured to control the self-refresh operation for the plurality ofmemory banks in response to the logical combination of the first addresssignal, the second address signal, and subblock refresh data generatedbased on the bits corresponding to each of the plurality of memory banksstored in the storage.
 36. The DRAM device of claim 35, wherein thesubblock address controlling circuit comprises a selecting circuitconfigured to produce selected addresses, the selected addressesproduced based on the first address signal in the self-refresh modeoperation and otherwise based on the second address signal.
 37. The DRAMdevice of claim 36, wherein the subblock address controlling circuitfurther comprises an address decoding circuit configured to decode theselected addresses to produce decoded addresses corresponding to each ofthe plurality of memory banks.
 38. The DRAM device of claim 37, whereinthe subblock address controlling circuit further comprises a subblockselecting circuit configured to logically combine the decoded addressesand the subblock refresh data to produce selected addresses designatingthe memory banks to be refreshed.
 39. A method for refreshing a dynamicrandom access memory (DRAM) device comprising a plurality memory bankseach having a plurality of wordlines, each of the plurality of wordlinesbeing connected to a plurality of data store cells that are refreshablein a self-refresh mode, the method comprising: controlling, in theself-refresh mode, the refreshing of each of the plurality of memorybanks independently from each other by: storing a bit corresponding toeach of the plurality of memory banks, each bit indicating whether ornot the corresponding memory bank is to be refreshed in the self-refreshmode; performing, in the self-refresh mode, a self-refresh operationonly for memory banks for which the corresponding bits indicate that thememory banks are to be refreshed.
 40. The method of claim 39, furthercomprising receiving a data input signal comprising bank selection inputdata corresponding to each of the plurality of banks, wherein the bitscorresponding to each of the plurality of memory banks are stored inresponse to corresponding bank selection input data.
 41. An apparatus,comprising: a controller operable to communicate with a dynamic randomaccess memory device (DRAM) comprising a plurality memory banks eachhaving a plurality of wordlines, each of the plurality of wordlinesbeing connected to a plurality of data store cells that are refreshablein a self-refresh mode, the controller operable to: generate a datainput signal to be communicated to the DRAM device, the data inputsignal configured to cause the DRAM device to store a bit correspondingto each of the plurality of memory banks, each bit indicating whether ornot the corresponding memory bank is to be refreshed in the self-refreshmode; generate a command signal comprising a plurality of commands, oneor more of the plurality of commands operable to cause the DRAM deviceto initiate the self-refresh mode in which a self-refresh operation isperformed only for memory banks for which the corresponding bitsindicate that the memory banks are to be refreshed.
 42. The apparatus ofclaim 41, wherein the data input signal comprises bank selection inputdata corresponding to each of the plurality of banks of the DRAM device.43. A method for controlling refreshing a dynamic random access memorydevice (DRAM) comprising a plurality memory banks each having aplurality of wordlines, each of the plurality of wordlines beingconnected to a plurality of data store cells that are refreshable in aself-refresh mode, the method comprising: generating a data input signalto be communicated to the DRAM device, the data input signal configuredto cause the DRAM device to store a bit corresponding to each of theplurality of memory banks, each bit indicating whether or not thecorresponding memory bank is to be refreshed in the self-refresh mode;generating a command signal comprising a plurality of commands, one ormore of the plurality of commands operable to cause the DRAM device toinitiate the self-refresh mode in which a self-refresh operation isperformed only for memory banks for which the corresponding bitsindicate that the memory banks are to be refreshed.
 44. The method ofclaim 43, wherein the data input signal comprises bank selection inputdata corresponding to each of the plurality of banks of the DRAM device.